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| author | Jens Axboe <axboe@kernel.dk> | 2019-12-25 16:33:42 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2020-01-20 17:03:59 -0700 |
| commit | ba04291eb66ed895f194ae5abd3748d72bf8aaea (patch) | |
| tree | 398b8455348b4b2a2171554f01447c74ffb9f28e /fs/io_uring.c | |
| parent | 3a6820f2bb8a079975109c25a5d1f29f46bce5d2 (diff) | |
| download | lwn-ba04291eb66ed895f194ae5abd3748d72bf8aaea.tar.gz lwn-ba04291eb66ed895f194ae5abd3748d72bf8aaea.zip | |
io_uring: allow use of offset == -1 to mean file position
This behaves like preadv2/pwritev2 with offset == -1, it'll use (and
update) the current file position. This obviously comes with the caveat
that if the application has multiple read/writes in flight, then the
end result will not be as expected. This is similar to threads sharing
a file descriptor and doing IO using the current file position.
Since this feature isn't easily detectable by doing a read or write,
add a feature flags, IORING_FEAT_RW_CUR_POS, to allow applications to
detect presence of this feature.
Reported-by: 李通洲 <carter.li@eoitek.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'fs/io_uring.c')
| -rw-r--r-- | fs/io_uring.c | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c index 407ba3388e14..5286620e4e46 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -495,6 +495,7 @@ struct io_kiocb { #define REQ_F_COMP_LOCKED 32768 /* completion under lock */ #define REQ_F_HARDLINK 65536 /* doesn't sever on completion < 0 */ #define REQ_F_FORCE_ASYNC 131072 /* IOSQE_ASYNC */ +#define REQ_F_CUR_POS 262144 /* read/write uses file position */ u64 user_data; u32 result; u32 sequence; @@ -1711,6 +1712,10 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe, req->flags |= REQ_F_ISREG; kiocb->ki_pos = READ_ONCE(sqe->off); + if (kiocb->ki_pos == -1 && !(req->file->f_mode & FMODE_STREAM)) { + req->flags |= REQ_F_CUR_POS; + kiocb->ki_pos = req->file->f_pos; + } kiocb->ki_flags = iocb_flags(kiocb->ki_filp); kiocb->ki_hint = ki_hint_validate(file_write_hint(kiocb->ki_filp)); @@ -1782,6 +1787,10 @@ static inline void io_rw_done(struct kiocb *kiocb, ssize_t ret) static void kiocb_done(struct kiocb *kiocb, ssize_t ret, struct io_kiocb **nxt, bool in_async) { + struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb); + + if (req->flags & REQ_F_CUR_POS) + req->file->f_pos = kiocb->ki_pos; if (in_async && ret >= 0 && kiocb->ki_complete == io_complete_rw) *nxt = __io_complete_rw(kiocb, ret); else @@ -6154,7 +6163,7 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p) goto err; p->features = IORING_FEAT_SINGLE_MMAP | IORING_FEAT_NODROP | - IORING_FEAT_SUBMIT_STABLE; + IORING_FEAT_SUBMIT_STABLE | IORING_FEAT_RW_CUR_POS; trace_io_uring_create(ret, ctx, p->sq_entries, p->cq_entries, p->flags); return ret; err: |